Research On Dropping Impact Characteristics Of Pears

The damage problem of fruit during storing and transporting is paid more and more attentions nowadays. Damage reducing by scientific methods is one of the most important subjects in the area of modern agricultural technology. Fruits are bruised by vibration, collision, impact, static compression and extrusion during harvesting handling, cleaning, classification and transportation. There are two damage styles, one is instant plastic damage and the other is lingering viscoelastic bruise. Dropping impact is one of the most important causes for fruits` damage.By taking dropping impact experiment using ShuiJing pear and Gong pear, the critical heights of bruise damage boundaries are got. A rheological viscoelastic model which depicts the dropping impact properties of pears is developed in this paper. The parameters of the model are calculated and validated by the dropping experiments. It is confirmed that the model is valid to describe the dropping impact characteristics of Shuijing pear and Gong pear, and the pertinences between theory and experiment is as high as 0.97.The nonlinear viscoelastic characteristics of corrugated paper and EPS are studied by static compression experiment. Combing theoretic analysis and experiment, a dynamic model which can describe both the above two cushion materials is got, and the parameters are also calculated and validated. The model is suitable to express the compression trait when the deformation is reparable; but not appropriate for describing the trait after the deformation is beyond retrieved. This model is more appropriate to describe the compression property of EPS than corrugated board.Dropping impact tests of fruits with cushion materials are designed based on the theories of viscoelastic characteristics of fruits and the compressibility of cushion materials. The dropping dynamic specialty of fruits with cushion materials and the different cushion capacity of corrugated paper and EPS are discussed in the paper. Under the same impact force, the deformation of pear is reduced more by using corrugated board as cushion material than using EPS. Therefore, corrugated board is more suitable than EPS to protect pear from bruise.The dropping impact dynamic response of fruits in two conditions of rigidity and cushion protection are discussed. After predigesting the dynamic response equation, Runge-Kutta integration method is invited to solve the equation. Meanwhile, the relation between deformation and time, velocity and time, acceleration and time of pears are educed respectively.With the help of these discussions the dropping bruise boundaries of pears and pears with corrugated paper and EPS are developed in this paper. At last the design and validation method for fruits'protection packaging is also presented as a pilot study.